Morihara Daichi, Moriya Jura, Kagitani Fusako, Uchida Sae
Department of Autonomic Neuroscience, Tokyo Metropolitan Institute for Geriatrics and Gerontology, Tokyo, Japan.
Department of Applied Life Science, United Graduate School of Agricultural Sciences, Tokyo University of Agriculture and Technology, Tokyo, Japan.
Eur J Neurosci. 2025 May;61(9):e70135. doi: 10.1111/ejn.70135.
Information about the sense of smell is conveyed by the olfactory nerve, or by the trigeminal nerve when irritating odors. We recently reported that olfactory nerve stimulation increases regional cerebral blood flow (BF) in the olfactory bulb, and the activation of nicotinic receptors in the brain potentiates olfactory bulb BF responses in anesthetized rats. This study aimed to elucidate the effects of intranasal trigeminal nerve stimulation on regional cerebral BF compared to the olfactory nerves, as well as the impact of nicotinic receptor activation on these BF responses. Regional BF in the olfactory bulb and frontal cortex was measured by laser Doppler flowmeter or laser speckle contrast imager in anesthetized and artificially ventilated rats. Electrical stimulation of the intranasal trigeminal nerve (0.5 ms, 5 mA, 20 Hz, and 5 s) produced a small increase in olfactory bulb BF and robust increases in both frontal cortical BF and arterial pressure. Transecting the upper thoracic spinal cord eliminated the pressor response, and although intranasal electrical stimulation did not elevate the olfactory bulb BF, it increased BF in the frontal cortex. Intravenous injection of nicotine (30 μg/kg), a nicotinic receptor agonist, did not influence the olfactory bulb BF but augmented increased BF in the frontal cortex following the intranasal trigeminal nerve stimulation. In conclusion, this study showed that the intranasal trigeminal nerve stimulation increased BF in the frontal cortex, but not in the olfactory bulb, independent of blood pressure changes. Furthermore, activation of nicotinic cholinergic transmission potentiated the frontal cortical BF responses to intranasal trigeminal stimulation.
嗅觉信息通过嗅神经传递，而刺激性气味则通过三叉神经传递。我们最近报道，嗅神经刺激可增加嗅球的局部脑血流量（BF），并且脑内烟碱受体的激活可增强麻醉大鼠嗅球BF反应。本研究旨在阐明与嗅神经相比，鼻内三叉神经刺激对局部脑BF的影响，以及烟碱受体激活对这些BF反应的影响。在麻醉和人工通气的大鼠中，用激光多普勒血流仪或激光散斑对比成像仪测量嗅球和额叶皮质的局部BF。鼻内三叉神经电刺激（0.5毫秒、5毫安、20赫兹和5秒）使嗅球BF略有增加，额叶皮质BF和动脉压显著增加。切断上胸段脊髓可消除升压反应，虽然鼻内电刺激未提高嗅球BF，但增加了额叶皮质的BF。静脉注射烟碱受体激动剂尼古丁（30微克/千克）对嗅球BF无影响，但增强了鼻内三叉神经刺激后额叶皮质BF的增加。总之，本研究表明，鼻内三叉神经刺激可增加额叶皮质而非嗅球的BF，且与血压变化无关。此外，烟碱胆碱能传递的激活增强了额叶皮质对鼻内三叉神经刺激的BF反应。
